Comprehensive test cases for the IsAssignableToGenericType test

IsAssignableToGenericTypeTests.cs

using System;
using System.Collections.Generic;

namespace klmr {
    // Version from http://stackoverflow.com/a/75502/1968
    public class Test {
        public static bool IsAssignableToGenericType(Type givenType, Type genericType) {
            var interfaceTypes = givenType.GetInterfaces();
            
            foreach (var it in interfaceTypes)
                if (it.IsGenericType)
                    if (it.GetGenericTypeDefinition() == genericType) return true;
            
            Type baseType = givenType.BaseType;
            if (baseType == null) return false;
            
            return baseType.IsGenericType &&
                baseType.GetGenericTypeDefinition() == genericType ||
                    IsAssignableToGenericType(baseType, genericType);
        }
    }
}

namespace jams {
    // Version from http://stackoverflow.com/a/1075059/1968
    class Test {
        public static bool IsAssignableToGenericType(Type givenType, Type genericType)
        {
            var its = givenType.GetInterfaces();
            
            foreach (var it in its)
            {
                if (it.IsGenericType && it.GetGenericTypeDefinition() == genericType)
                    return true;
            }
            
            if (givenType.IsGenericType && givenType.GetGenericTypeDefinition() == genericType)
                return true;
            
            Type baseType = givenType.BaseType;
            if (baseType == null) return false;
            
            return IsAssignableToGenericType(baseType, genericType);
        }
    }
}

namespace TestRunner {
    class Base<T> { }

    interface IBase<T> { }

    interface IDerived<T> : IBase<T> { }

    class Derived<T> : Base<T>, IBase<T> { }

    class Derived2<T> : Derived<T> { }

    class DerivedI<T> : IDerived<T> { }

    class Tests {
        static void Main() {
            Console.WriteLine("# Base class");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Base<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Base<>)));
            
            Console.WriteLine("# Interface");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(List<int>), typeof(IEnumerable<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(List<int>), typeof(IEnumerable<>)));

            Console.WriteLine("# Self");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Derived<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Derived<>)));

            Console.WriteLine("# Transitive base class");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived2<int>), typeof(Base<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived2<int>), typeof(Base<>)));

            Console.WriteLine("# Transitive interface");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(DerivedI<int>), typeof(IBase<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(DerivedI<int>), typeof(IBase<>)));

            Console.WriteLine("# Transitive base class to interface");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived2<int>), typeof(IBase<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived2<int>), typeof(IBase<>)));

            Console.WriteLine("# Nullable type");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(int?), typeof(Nullable<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(int?), typeof(Nullable<>)));

            Console.WriteLine("# Negative control: non-generic base");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Object)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Object)));

            Console.WriteLine("# Negative control: non-base class");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(List<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(List<>)));

            Console.WriteLine("# Negative control: non-base interface");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(IEnumerable<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(IEnumerable<>)));

            Console.WriteLine("# Negative control: concrete class");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Base<int>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(Derived<int>), typeof(Base<int>)));

            Console.WriteLine("# Negative control: concrete interface");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(List<int>), typeof(IEnumerable<int>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(List<int>), typeof(IEnumerable<int>)));

            Console.WriteLine("# Negative control: non-nullable type");
            Console.WriteLine(klmr.Test.IsAssignableToGenericType(typeof(int), typeof(Nullable<>)));
            Console.WriteLine(jams.Test.IsAssignableToGenericType(typeof(int), typeof(Nullable<>)));
        }
    }
}